Internal combustion engines combust an air/fuel mixture to produce drive torque. More specifically, air is drawn into cylinders of the engine and is combined with fuel therein. The air/fuel mixture is compressed by a piston and is ignited to drive the piston within the cylinder. The combustion product or exhaust is exhausted from the cylinder and a fresh air/fuel mixture is prepared for subsequent combustion. Engine pumping work is required to drive the intake and exhaust, which detracts from the engine torque output. Therefore, engine pumping work must be considered when regulating engine operation.
A valvetrain regulates air intake and exhaust to and from the cylinders. Traditional engines include fixed valvetrains, whereby intake and exhaust valve opening and closing occur relative to respective crankshaft angles. Thus, traditional engine control systems incorporate calibrated look-up tables that provide engine operation information including, but not limited to, engine pumping work. In this manner, engineers calibrate look-up tables for a specific engine type, and the engine control system regulates operation of the engine based on the look-up table.
However, more modern engine control systems have become increasingly complex. For example, engines can include variable lift and valve timing mechanisms that adjust intake and exhaust valve opening and closing relative to the crankshaft angle based on engine operating conditions. As a result, look-up calibration for adjustable valvetrain engines has been compounded, which increases overall system cost. Alternatively, the look-up tables have been simplified. This, however, decreases accuracy of engine operation.